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. Questions and Answers. The Internet Journal of Anesthesiology. 1998 Volume 3 Number 4.
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What is P-50 in the oxyhemoglobin dissociation curve?
What are the absolute and relative contraindications for spinal anesthesia?
P-50 is the oxygen tension (PaO2) associated with 50% hemoglobin saturation. Under normal conditions (pH 7.4, PaCo2 40 mmHg, 37 degree C) it has a value of 26.6 mmHg.
A left shift of the curve caused by alkalosis, hypothermia, abnormal Hb, hypocarbia, and low 2,3 DPG-levels results in a greater affinity of hemoglobin for oxygen (oxygen is less likely to be released into the tissue).
A right shift of the curve caused by acidosis, hyperthermia, hypercarbia, and high 2,3 DPG-levels results in a lower affinity of hemoglobin for oxygen (oxygen is more likely to be released into the tissue).